The present invention relates to a polyamide elastomer consisting essentially of a segmented polyether-ester-amide and more particularly to a polyamide elastomer which exhibits superior rubber elasticity, mechanical strength and moldability over a wide temperature range from low to high temperature.
Polyether-ester-amide block copolymers are known that they are thermoplastic elastomers having superior impact resistance and rubber elasticity like polyether esters and polyether amides. For example, a polyether-ester-amide comprising polydodecaneamide (nylon 12) as hard segment and poly(tetramethylene oxide) glycol as polyether component is presently available commercially. This block copolymer is superior in flexibility and impact resistance at low temperatures, but its high-temperature characteristics and oil- and chemicals-resistance are not satisfactory. Especially at a high temperature region not lower than 100.degree. C., a conspicuous deterioration is observed with respect to elastic modulus and strength, and at temperatures not lower than 120.degree. C. it is substantially impossible to use such commercially available polyether-ester-amide.
In an attempt to improve high-temperature characteristics of polyether-ester-amide there has been proposed one which employs polycapramide (nylon 6) as hard segment. But the affinity of nylon 6 for such a polyether as poly(tetramethylene oxide) glycol is low and so its copolymerizable composition range is limited; besides, it is necessary that the caprolactam should be distilled out of the reaction system during melt polymerization, thus it being difficult to produce on an industrial scale a polyether-ester-amide of a desired composition and of a high polymerization degree. Under the circumstances, with such polyether-ester-amide using nylon 6 as hard segment, an elastomer superior in both flexibility and high-temperature characteristics has not been obtained yet. In the case of a soft type polyether-ester-amide using nylon 6 as hard segment and containing a larger amount of polyether component, the deterioration of crystallinity is conspicuous and also from this point it is difficult to attain both high-temperature characteristics and flexibility.
There has been proposed a process for preparing a polyether-ester-amide by reacting a dicarboxylic polyamide (nylon 6-12 component), obtained from hexamethylenediamine-dodecanoate and adipic acid, with polytetramethylene glycol (U.S. Pat. No. 4,230,838).
However, most of the polyether-ester-amides concretely disclosed therein using as hard segment polyamide in which the total number of carbon atoms of diamine and dicarboxylic acid is not less than 16 have melting points lower than 160.degree. C. Even a polyether-ester-amide having a melting point higher than 160.degree. C., the elastic recovery is low and the tensile strength at elevated temperatures, for instance, 120.degree. C. or more is lower than 50 kg/cm.sup.2. Therefore, they are unsuitable for use in automobile hose or the like.